[MSUE-232] - Add typing. Apply code linters. Update documentation

[pecheneff]

Purpose

Make Sift's API client for Python type safe and actualize doc strings of the client's methods.

Summary

• Deprecated support of Python versions < 3.8
• Added typing annotations overall the library
• Updated client methods' doc strings with actual information
• Replaced legacy API URLs with actual API URL "https://api.sift.com"
• Reworked library's packaging with pyproject.toml
• Integrated pre-commit hooks with Python code linters
• Fixed small issue when the client could send requests with invalid version in the User-Agent header

Testing

Python 3.8

Python 3.9

Python 3.10

Python 3.11

Python 3.12

Python 3.13

Checklist

• The change was thoroughly tested manually
• The change was covered with unit tests
• The change was tested with real API calls (if applicable)
• Necessary changes were made in the integration tests (if applicable)
• New functionality is reflected in README